Synthesis and Preclinical Evaluation of 99mTc-Labeled Benzenesulfonamides for SPECT Imaging of Carbonic Anhydrase IX Expression

Carbonic anhydrase IX (CA-IX) is overexpressed in clear cell renal cell carcinoma (ccRCC) and hypoxic tumors, and is regarded as a potential target for tumor diagnosis and treatment. In this work, two ligands (HA and HFA) that contain HYNIC and benzenesulfonamide were designed and synthesized. Four 99mTc-labeled complexes with high labeling yields and good in vitro stability were obtained and evaluated. In the cell binding assay, the [99mTc]Tc-HA-TPPTS and [99mTc]Tc-HFA-TPPTS complexes showed higher targeting specificity and affinity for CA-IX than the other radiotracers. The micro-SPECT images and biodistribution results revealed that the [99mTc]Tc-HA-TPPTS complex had high tumor specific uptake and target-nontarget ratios at 60 min p.i. (tumor-to-blood ratio: 4.85 ± 0.09 and tumor-to-muscle ratio: 11.31 ± 1.37) and exhibited the ability to visualize tumors in nude mice bearing HT-29 tumors. Therefore, these results demonstrated that [99mTc]Tc-HA-TPPTS is a promising candidate probe targeting CA-IX for tumor imaging.